Agent and method for permanent shaping of hair and method for the production of N-alkylmercaptoacetamides

ABSTRACT

The aqueous ready-to-apply composition for permanent waving of hair has a pH of 4 to 8.5 and from 3 to 28% by weight of at least one N-alkylmercaptoacetamide of formula (I):                    
     wherein R represents a straight-chain alkyl group having from 3 to 6 carbon atoms or a straight-chain hydroxyalkyl group having from 3 to 6 carbon atoms; or a salt thereof; and at least one standard cosmetic additive ingredient, such as thickeners, wetting agents and emulsifiers, perfume oils, conditioners and buffer substances. The ready-to-apply composition can be made by mixing two or more components, one of which contains the N-alkylmercaptoacetamide. A method for permanent waving of hair using the ready-to-apply composition is also described. A process for making the N-alkylmercapto-acetamides includes reacting a suitable amine with methylthioglycolate under a protective gas atmosphere at temperatures that are not greater than 30° C.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composition for permanent hair wavingbased on straight-chain N—C₃—to N—C₃-C₆-alkyl- orN—C₃-C₆-hydroxyalkyl-substituted mercaptoacetamides, as thekeratin-reducing ingredient, and to a method for permanent hair wavingusing this composition.

2. Prior Art

The classic technique for permanent hair waving is familiarly based ontwo treatment steps: In the first step, the cystine-disulfide bridges ofthe keratin of the hair are opened by the action of an agent thatcontains a reducing ingredient (waving composition). The hair is thenput into the desired form. In a second step, cystine-disulfide bonds areclosed again using a fixative, that is, an agent containing an oxidantingredient.

As the pioneering work in German patents 948 186 and 972 424demonstrate, thioglycolic acid, for instance in the form of an ammoniumor monoethanolamine salt, is used as a classic permanent hair wavingreducing agent. Other typical reducing agents are 2-mercaptopropionicacid (thiolactic acid), 3-mercaptopropionic acid, cysteine, andderivatives of these compounds, as well as certain mercaptocarboxylicacid esters.

Alkaline-adjusted preparations based on mercaptocarboxylic acid esters,despite being adequately effective, cause hair damage, which isexpressed for instance in increased hair breakage. Often, thesecompositions also undesirably stress the scalp. Finally, the unpleasantodor of the reducing agents used requires intensive perfuming of theproducts. By using 2-mercaptopropionic acid, it is possible to solvesome of these problems. However, in comparison to thioglycolic acid,which is widely used, thiolactic acid produces weaker waves.

For gentle, permanent waving of damaged and especially bleached or dyedhair, waving compositions that are adjusted to be slightly acidic toneutral are preferably used. From a professional standpoint, over thelast 35 years, the thioglycolic acid esters have proved to be thereducing agents best suited for this purpose.

A major disadvantage of acidic hair waving compositions based onthioglycolic acid esters, however, is that they are poorly tolerated bythe eyes and skin, and the sensitizing effect of the thioglycolic acidesters, so that the use of these hair waving compositions is widelyavoided at present. Instead of the mercaptocarboxylic acid esters,mercaptoacetamides such as thioglycolic acid amide or alkyl- orhydroxyalkyl-substituted amides have also been used. Such compounds areknown from German Patent DE-C1 144 440 and European Patent EP-A 0 455457. Like the mercaptocarboxylic acid esters, these substances have ahigh waving potential at low pH values, but in terms of toxicology theyare even more critical than the mercaptocarboxylic acid esters.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to make available acomposition and a method for permanent hair waving that both in theacidic and the slightly alkaline range (pH—2 to 9.5), and above all inthe pH range from 4.0 to 8.5, makes gentle, uniform hair wavingpossible, has no or only a slight sensitizing potential, and furthermorehas a stronger hair waving potential than 2-mercaptopropionic acid(thiolactic acid).

Surprisingly, it has now been discovered that the above disadvantagescan be overcome by the use of certain N-alkylmercaptoacetamides, andthat they have a stronger hair waving potential than thiolactic acid.

The subject of the present invention is therefore a composition forpermanent hair waving, which is characterized in that as itskeratin-reducing ingredient, it contains an N-alkylmercaptoacetamide ofthe formula

in which R stands for a straight-chain alkyl radical with from 3 to 6carbon atoms, or a straight-chain hydroxyalkyl radical with from 3 to 6carbon atoms, or its salt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferably, the straight-chain hydroxyalkyl radical has one or twohydroxyl groups.

Preferred N-alkylmercaptoacetamides of formula (I) areN-propyl-2-mercaptoacetamide, N-(2′-hydroxypropyl)-2-mercaptoacetamide,and N-(3′-hydroxypropyl)-2-mercaptoacetamide.

Possible salts include above all the hydrogen salts of the acids in thegroup comprising hydrochloric acid, sulfuric acid, acetic acid or citricacid.

The N-alkylmercaptoacetamide of formula (I) is preferably contained asthe sole keratin-reducing ingredient in the composition. However, it mayalso be used in combination with other keratin-reducing ingredients—suchas thioglycolic acid, thiolactic acid, 2-hydroxy-3-mercaptopropionicacid, cysteamine and cysteamine derivatives such as alkyl- oracylcystamine or cysteine and cysteine derivatives, such ascysteine-(2-hydroxyethyl)ester or L-cysteine glycerine ester orsulfites.

The N-alkylmercaptoacetamide of formula (I) is contained in theready-to-use composition for permanent hair waving in a quantity of from3 to 28 weight-%, preferably 5 to 21 weight-%.

The ready-to-use hair waving composition preferably has a pH value offrom 2.0 to 9.5 and especially preferably from 4.0 to 8.5. As analkalizing agent or agent for adjusting the pH value, ammonia or causticsoda is especially suitable, but water-soluble, physiologicallytolerable salts of organic and inorganic bases can also be considered,such as ammonium hydrogen carbonate. To establish an acidic pH value,hydrochloric acid, acetic acid or citric acid can be used in particular.

The waving composition may be sold in single- or dual- ortriple-component packages; the composition may be in the form of anaqueous solution, or an emulsion, or in thickened water-based form,especially a creme, gel, foam or paste.

It is understood that the waving composition may contain all the usualand known additives for such compositions, such as thickeners, such asbentonite, fatty acids, starch, polyacrylic acid and its derivatives,cellulose derivatives, alginates, vaseline, and paraffin oils; wettingagents or emulsifiers from the classes of anionic, cationic, amphotericor nonionic surfactants, such as fatty alcohol sulfates, fatty alcoholether sulfates, alkyl sulfonates, alkylbenzene sulfates, quaternaryammonium salts, alkyl betaines, ethoxylated alkylphenols, fatty acidalkanolamides or ethoxylated fatty acid esters; and opacifiers, such aspolyethyleneglycol esters; alcohols, such as ethanol, propanol,isopropanol, polyols such as 1,2- or 1,2-propanediol, 1,2-, 1,3- or1,4-butanediol, 1,2-pentanediol and glycerine; sugars such as D-glucose;solubilizers, stabilizers, buffer substances, perfume oils, dyes, andhair-conditioning and hair-care ingredients, such as cationic polymers,lanolin derivatives, cholesterol, pantothenic acid, and betaine.

The aforementioned ingredients are used in quantities usual for suchpurposes; for example, the wetting agents and emulsifiers inconcentrations of a total of 0.2 to 30 weight-%, the alcohols in a totalquantity of 0.1 to 20 weight-%, the opacifiers, perfume oils and dyes ina quantity of 0.01 to 1 weight-% each, the buffer substances in a totalquantity of 0.1 to 10 weight-%, and sugars, solubilizers, stabilizersand hair-conditioning and hair-care ingredients in a quantity of 0.1 to5 weight-% each, while the thickeners and solubilizers may be containedin this composition in a total quantity of 0.5 to 20 weight-%.

So-called swelling agents and penetrating substances can also be addedto this composition, examples being dipropyleneglycol monomethyl ether,2-pyrrolidone or imidazolidin-2-one, in a quantity of 1 to 30 weight-%,and to avoid making the hair too kinky, dithio compounds, such asdithioglycolic acid, dithiolactic acid, the disulfides of thesecompounds, or their salts.

By varying the pH value, a composition can be made available that isuniversally suitable for every hair structure, optionally with theadditional application of heat. The composition brings about an elastic,durable and uniform waving from the root of the hair to the ends,without eliciting allergic or sensitizing reactions.

The present invention also relates to a method for permanent hairwaving, in which before and/or after the hair is set in the desired way,the hair is treated with a waving composition, rinsed with water, thenoxidatively treated, rinsed with water, optionally set for water wavingand then dried, which is characterized in that as the wavingcomposition, the compositions of the invention as described above areused.

In a preferred embodiment of the method of the invention, the hair isfirst washed with a shampoo and then rinsed with water. Next, thetowel-dried hair is divided into individual strands and wound ontocurlers with a diameter of 5 to 30 millimeters, preferably 5 to 15millimeters. The hair is then treated with an adequate quantity for hairwaving, preferably 60 to 120 grams, of the described waving compositionof the invention.

After an action time sufficient for the permanent waving of the hair,which depending on the nature of the hair, on the pH value and thewaving effectiveness of the waving composition, and on the temperatureemployed amounts to from 5 to 30 minutes (10 to 30 minutes if heat isnot applied; 5 to 20 minutes with the application of heat), the hair isrinsed with water and then oxidatively post-treated (“fixed”). Thepost-treatment composition is used in a quantity of preferably 80 to 100grams, depending on the fullness of the hair.

For the oxidative post-treatment, with the hair either wound up oncurlers or not, any arbitrary post-treatment composition suitable forsuch a treatment can be used. Examples of oxidants that can be used insuch post-treatment compositions are potassium bromate, sodium bromate,sodium perborate, urea peroxide and hydrogen peroxide. The concentrationof the oxidant varies, depending on the application time (as a rule, 5to 15 minutes) and the application temperature. Normally, the oxidant ispresent in the ready-to use aqueous post-treatment composition in aconcentration of 0.5 to 10 weight-%. The composition for oxidativepost-treatment can naturally also include other substances, such aswetting agents, hair-care substances such as cation-active polymers,weak acids, buffer substances or peroxide stabilizers, and may be in theform of a aqueous solution, an emulsion, or a thickened water-basedform, in particular a creme, gel or paste. These typical additives maybe contained in the post-treatment composition in a quantity of 0.1 to10 weight-%, in particular. Next, the curlers are removed. If necessary,the hair after being taken down from the curlers is oxidativelypost-treated yet again. The hair is then rinsed with water, optionallyset for a water wave, and finally dried.

Completely surprisingly, the preferred N-alkylmercaptoacetamides, whichare N-propyl-2-mercaptoacetamide,N-(2′-hydroxypropyl)-2-mercaptoacetamide, andN-(3′-hydroxypropyl)-2-mercaptoacetamide, have substantially lowersensitization rates than their closest relatives in permanent wavingingredients, the N-alkylmercaptoacetamides known from the prior art asdefined by German Patent DE-C1 144 440 and European Patent EP-A 0 455457, that is, N-methylmercaptoacetamide andN-hydroxyethylmercaptoacetamide.

The production of the N-alkylmercaptoacetamide of formula (I) is done byreacting the corresponding amine at a temperature of not over 30° C.with methylthioglycolate in a protective gas atmosphere, extraction in asuitable solvent, and ensuing flash distillation.

The following examples are intended to explain the subject of theinvention in further detail, but without limiting the subject to theseexamples.

PRODUCTION EXAMPLES Example 1 Production of N-Propyl-2-mercaptoacetamide

118 g (2 mol) of n-propylamine are first put in a 500-ml three-neckflask. Slowly, 106.24 g of methylthioglycolate are added drop by drop,in such a way that the temperature does not exceed 30° C. The startingmixture is flushed with argon and stirred for 2 days at roomtemperature.

The mixture is acidified (pH 2-4) with 36% hydrochloric acid while beingchilled with ice and is then extracted to exhaustion using ethylacetate. The solvent is distilled off in a vacuum in the refluxevaporator; the residue is brought to a pH of 7.0 by adding caustic sodaand then shaken out again with ethyl acetate. The combined fractions aredried over sodium sulfate and inspissated. The residue then is distilledinto the pure product by flash distillation at a maximum of 0.01 Torr.The yield is 115 g (86%).

Analysis:

a) ¹H-NMR (CDCl₃):

δ (ppm) 6.79 (bulbous, —NH) 3.20 (t, 2H, + NH—CH₂) 3.20 (s, 2H,HS—CH₂—CO) 1.85 (bulbous, 1H, HS) 1.52 (m, 2H, NH—CH—CH₂) 0.90 (t, 2H,CH₂—CH₃)

b) ¹³C-NMR (CDCl₃):

δ (ppm) 169.18 (—C═O) 41.83 (NH—CH) 28.36 (HS—CH₂) 22.72 (NH—CH—CH₂—CH₃)11.37 (CH₂—CH₃)

c) MS (70 e V, EI, RT)

m/z (%)=

(M⁺)=133 (47.68) 100 (29.1), 86 (24.58), 58 (8.6), 47 (25.67), 43 (100)

d) Thioltitration: 95.78%

e) Elemental analysis: C₅H₁₁NOS (MW: 133.21)

Calculated: C 45.08, H 8.32, N 10.51, S 24.07

Found: C 44.72, H 8.12, N 10.18, S 23.71

f) IR (NaCl slides)

3293s (NH) 3084-2876s (CH₂) 2552w (SH) 1652s (N-monosubstituted amide)1559s (N-monosubstituted amide)

g) HPLC: The results of the HPLC showed 98.07 area % for the compound.

(Column: C 18 5U, 250 mm×4.6 mm; flow agent acetonitrile:buffer[4 gKH₂PO₄+0.8 g octanesulfonic acid sodium salt+2 ml H₃PO₄]=25: 75; flowrate 0.5 ml/min; wavelength 200 nm)

h) pKs: 8.451 (H₂O)

i) UV-max: 209.8 nm (acetonitrile:buffer=25:75)

i) Boiling point: 76° C. at 0.01 Torr

Example 2 Production of N-(2′-Hydroxypropyl)-2-mercaptoacetamide

150.22 g (2 mol) of 1-amino-2-propanol are first put in a 500-mlthree-neck flask. Slowly, 106.24 g (1 mol) of mercaptoacetic acid methylester are added drop by drop, in such a way that the temperature doesnot exceed 30° C. The starting mixture is flushed with argon and stirredfor 2 days at room temperature.

The mixture is acidified (pH 2-4) with 36% hydrochloric acid while beingchilled with ice and is then extracted to exhaustion using ethylacetate. The solvent is distilled off in a vacuum in the refluxevaporator; the residue is brought to a pH of 7.0 by adding caustic sodaand then shaken out again with ethyl acetate. The combined fractions aredried over sodium sulfate and inspissated. The applicable residue isdistilled into the pure product by flash distillation at a maximum of0.01 Torr. The yield is 95 g (64%).

Analysis:

a) ¹H-NMR (CDCl₃):

δ_(H) (ppm) 6.70 (bulbous, —NH) 3.93 (m, 1H, CH) 3.44 and 3.14 (m, 1Heach, NH—CH ₂) 3.26 (s, 2H, HS—CH ₂—CO) 2.07 (t, 1H, HS) 1.21 (d, 3H,CH₃)

b) ¹³C-NMR (CDCl₃):

δ_(C) (ppm) 170.71 (—C═0) 67.00 (NH—CH₂—CH) 47.38 (NH—CH ₂) 28.24(HS—CH₂) 20.87 (CH ₃)

c) MS (70 e V, EI, RT)

m/z (%)=

(M⁺)=149 (8.39) 131 (47.08), 105 (100), 84 (27.49), 72 (72.76), 58(57.75), 56 (32.11), 47 (59.94)

d) Thioltitration: 97.88%

e) Elemental analysis: C₆H₁₃NOS (MW: 149.21)

Calculated: C 40.25, H 7.43, N 9.39, S 21.49

Found: C 40.11, H 7.42, N 9.12, S 21.53

f) IR (KBr)

3314s (OH) 3090-2927s (CH₂) 2549w (SH) 1657s (N-monosubstituted amide)1554s (N-monosubstituted amide)

g) HPLC: The results of the HPLC showed 98.88 area % for the compound.

(Column: C 18 5U, 250 mm×4.6 mm; flow agent acetonitrile:buffer[4 gKH₂PO₄+0.8 g octanesulfonic acid sodium salt+2 ml H₃PO₄]=25:75; flowrate 0.5 ml/min; wavelength 200 nm)

h) pKs: 7.865 (H₂0)

i) UV-max: 218.0 nm (acetonitrile:buffer=25:75)

i) Boiling point: 108° C. at 0.01 Torr

Example 3 Production of N-(3′Hydroxypropyl)-2-mercaptoacetamide

150.22 g (2 mol) of 3-amino-1-propanol are first put in a 500-mlthree-neck flask. Slowly, 106.24 g (1 mol) of mercaptoacetic acid methylester are added drop by drop, in such a way that the temperature doesnot exceed 30° C. The starting mixture is flushed with argon and stirredfor 2 days at room temperature.

The mixture is acidified (pH 2-4) with 36% hydrochloric acid while beingchilled with ice and is then extracted to exhaustion using ethylacetate. The solvent is distilled off in a vacuum in the refluxevaporator; the residue is brought to a pH of 7.0 by adding caustic sodaand then shaken out again with ethyl acetate. The combined fractions aredried over sodium sulfate and inspissated. The applicable residue isdistilled into the pure product by flash distillation at a maximum of0.01 Torr. The yield is 63 g (42%).

Analysis:

a) ¹H-NMR (CDCl₃):

δ_(H) (ppm) 7.062 (bulbous, —NH) 3.64 (m, 2H, CH₂—OH) 3.42 (m, 2H, CH₂—CH₂—CH₂—OH) 3.22 (d, 2H, HS—CH ₂—CO) 2.04 (t, 1H, CH₂—OH) 1.72 (t, 1H,HS) 1.69 (m, 2H, CH₂—CH ₂—CH₂—OH)

b) ¹³C-NMR (CDCl₃):

δ_(C)(ppm) 170.59 (—C═O) 59.86 (NH—CH₂) 37.06 (CH ₂—OH) 31.99 (CH₂—CH₂—CH₂—OH) 28.53 (HS—CH ₂)

c) MS (70 e V, EI, RT)

m/z (%)=

(M⁺)=149 (36.13) 131 (36.58), 116 (31.62), 105 (23.15), 102 (100), 84(72.8), 76 (24.49), 56 (66.29)

d) Thioltitration: 94.063%

e) Elemental analysis: C₅H₁₁NOS (MW: 149.21)

Calculated: C 40.25, H 7.43, N 9.39, S 21.49

Found: C 40.21, H 6.99, N 9.05, S 21.53

f) IR (NaCl)

3299s (NH) 3086-2918s (CH₂) 2546w (SH) 1651s (N-monosubstituted amide)1551s (N-monosubstituted amide)

g) HPLC: The results of the HPLC showed 93.19 area % for the compound.

(Column:C 18 5U, 250 mm×4.6 mm; flow agent acetonitrile:buffer[4 gKH₂PO₄+0.8 g octanesulfonic acid sodium salt+2 ml H₃PO₄]=25:75; flowrate 0.5 ml/min; wavelength 200 nm)

h) pKs: 8.406 (H₂0)

i) UV-max: 223.2 nm (acetonitrile:buffer=25:75)

i) Boiling point: 115° C. at 0.01 Torr

Example 4 Comparison of Waving Effectiveness

The waving effectiveness of the compound was determined, using glycerinemonothioglycolate as a comparison substance, using 10 waving solutionsat a pH of 7, 8 and 9. Counted strands of previously bleached and thusdamaged Central European hair (approximately 100 hairs per strand) 16.5centimeters in length were wound up, wet, onto spiral curlers (insidediameter: 3 millimeters) and after conditioning in a climate-controlledroom (temperature 20° C; humidity 65%) treated with a solutioncontaining 87 mmol/100 g of reducing agent, adjusted to the applicablepH value. The quantity of waving fluid applied was calculated using theratio 1:1.2 (1 g hair:1.2 ml waving fluid). 20 minutes was selected asthe action time; the action temperature was 50° C. The hair was thenfixed with a fixative containing peroxide and dried, and after beingtaken down from the curlers the hair was suspended in water for fourhours (water bath temperature 40° C.).

The wave stability is calculated by the following formula:${{Wave}\quad {stability}},{{{in}\quad \%} = {\frac{l_{o} - l_{t}}{l_{o} - l_{1}} \times 100}}$

where

l_(o) is the total length of the unwaved, straight strand (16.5centimeters)

l_(t) is the length of the strands after removal from the curlers andafter being hung out for 240 minutes

l₁ is the length of the unwaved, straight strand (35 centimeters, for aninside diameter of the curlers of 3 millimeters)

TABLE 1 Yield Elemental Analysis Waving ingredient in % calculated/foundN-Propyl-2- 86 C 45.08, H 8.32, mercaptoacetamide N 10.51, S 24.07/ C44.72, H 8.12, N 10.18, S 23.71 N-(2′-Hydroxypropyl)- 64 C 40.25, H7.43, 2-mercaptoacetamide N 9.39, S 21.49/ C 40.25, H 7.30, N 9.16, S21.63 N-(3′Hydroxypropyl)- 42 C 40.25, H 7.43, 2-mercaptoacetamide N9.39, S 21.49/ C 40.21, H 6.99, N 9.05, S 21.32 Thiolactic acid(2-mercaptopropionic acid) for comparison WSN WSN WSN HPLC pH = 7 pH = 8pH = 9 Waving ingredient (area %) BP in % in % in % N-Propyl-2- 98.06976° C. 85 96 100 mercaptoacetamide 0.01 Torr N-(2′-Hydroxypropyl)- 98.88108° C. 92 97 97 2-mercaptoacetamide 0.01 Torr N-(3′Hydroxypropyl)-93.19 115° C. 84 89 99 2-mercaptoacetamide 0.01 Torr Thiolactic acid 3854 62 (2-mercaptopropionic acid) for comparison

As the standard, strands were treated with a glycerine monothioglycolatesolution adjusted to pH 9. The standardized waving stabilities (WSN)given above in Table 1 pertain to this standard solution (pH=9), whosewave stability was taken as 100%.

Table 1 shows that at pH 7, 8, and 9, the waving effectiveness of themercaptoacetamides of the invention are higher than with thiolacticacid.

Examples of Permanent Waving Compositions Example 5 Permanent WavingComposition for Dyed Hair

10.8 g N-Propyl-2-mercaptoacetamide 0.4 g Ammonia (25% aqueous solution)for pH adjustment 2.0 g Ammonium hydrogen carbonate 5.0 g Isopropanol2.5 g 1,2-Propylene glycol 2.5 g 1,2-Pentanediol 1.0 g Isooctylphenol,ethoxylated with 10 Mol ethylene oxide 1.0 g Poly(dimethyldiallyammoniumchloride) 0.3 g Perfume oil 0.1 g Vinylpyrrolidone/styrene mixed polymer(Antara^(R) 430, GAF Corp., New York) 74.4 g Water 100.0 g The pH ofthis composition is 7.3.

Hair previously damaged by coloring treatments is washed with a shampoo,towel-dried, and set on curlers with a diameter of 8 millimeters. Next,the hair waving composition described above is applied evenly to thehair wound on the curlers. The hair is then covered with a plastic hoodand heated for 10 minutes under a dryer hood at a temperature of 45° C.The covering is then removed; the hair is rinsed with water andoxidatively post-treated with 100 grams of a 3% aqueous hydrogenperoxide solution. After the curlers are taken out, the hair is rinsedagain with water, set for a water wave, and then dried.

The result of this treatment is a uniform, elastic and durable waving ofthe hair.

Example 6 Permanent Waving Composition for Normal Hair

14.5 g N-Propyl-2-mercaptoacetamide 8.9 g Ammonia (25% aqueous solution)4.0 g Ammonium hydrogen carbonate 1.0 g 1,3-butanediol 5.0 g1,2-Propylene glycol 2.0 g Dipropyleneglycol monoethyl ether 4.0 g Urea2.5 g Hydrogenated castor oil, ethoxylated with 40 Mol ethylene oxide2.5 g Lauryl alcohol, ethoxylated with 40 Mol ethylene oxide (CTFA:Laureth-4) 0.5 g Perfume oil 0.1 g Vinylpyrrolidone/styrene mixedpolymer (Antara^(R) 430, GAF Corp., New York) 55.0 g Water 100.0 g ThepH of this composition is 8.4.

Normal hair, not previously damaged, is washed, dried with a hand towel,and wound onto curlers with a diameter of 6 millimeters. After that thehair is moistened thoroughly and evenly with the above-described hairwaving composition. After an action time of 15 minutes, the hair isrinsed thoroughly with water and then oxidatively post-treated with 80grams of a 3% aqueous hydrogen peroxide solution. After the curlers aretaken out, the hair is rinsed again with water, set for a water wave,and then dried. The thus-treated hair has a uniform, lively curliness.

Example 7 Permanent Waving Composition for Normal Hair

7.7 g N-Propyl-2-mercaptoacetamide 8.7 gN-(2′-Hydroxypropyl)-2-mercaptoacetamide 8.9 g Ammonia (25% aqueoussolution) for pH adjustment 5.0 g Ammonium hydrogen carbonate 1.0 g1,2-propanediol 2.0 g D-Glucose 2.4 g Ammonia 1.5 g Isooctylphenol,ethoxylated with 10 Mol ethylene oxide 0.5 g Poly(dimethyldiallyammoniumchloride) 0.5 g Perfume oil 0.1 g Vinylpyrrolidone/styrene mixed polymer(Antara^(R) 430, GAF Corp., New York) 61.7 g Water 100.0 g The pH ofthis composition is 8.3.

Normal hair, not previously damaged, is washed, dried with a hand towel,and wound onto curlers with a diameter of 6 millimeters. After that thehair is moistened thoroughly and evenly with the above-described hairwaving composition. After an action time of 15 to 25 minutes, the hairis rinsed thoroughly with water and then oxidatively post-treated with80 grams of a 3% aqueous hydrogen peroxide solution. After the curlersare taken out, the hair is rinsed again with water, set for a waterwave, and then dried. The thus-treated hair has a uniform, livelycurliness.

Example 8 Dual-Component Permanent Waving Composition for Normal Hair

Component A 4.5 g Ammonium hydrogen carbonate 0.4 g Ammonia (25% aqueoussolution) for pH adjustment 2.0 g Diethyleneglycol monoethyl ether 2.0 g1-Methoxypropanol 1.5 g Propylene glycol 0.5 g Oleyl alcoholpolyethyleneglycol ether - 5EO (CTFA: OLETH-5) 0.5 g Quaternary ammoniumsalt of the terpolymer of acrylic acid/diallyldimethylammonium chloride/acrylamide (CTFA: POLYQUATERNIUM-39) Trade name: Merguat^(R) Plus 33300.5 g Perfume oil 88.1 g Water 100.0 g Component B 50.0 gN-(2′-Hydroxypropyl)-2-mercaptoacetamide, 94% strength

For the use of the dual-component permanent waving composition, 60 g ofcomponent A is mixed with 14 g of component B to make a hair wavingcomposition that is ready to use. The mixing produces a product with apH of 6.5.

Normal hair, not previously damaged, is washed, dried with a hand towel,and wound onto curlers with a diameter of 6 millimeters. After that thehair is moistened thoroughly and evenly with the above-described hairwaving composition. After an action time of 15 to 25 minutes, the hairis rinsed thoroughly with water and then oxidatively post-treated with80 grams of a 3% aqueous hydrogen peroxide solution. After the curlersare taken out, the hair is rinsed again with water, set for a waterwave, and then dried. The thus-treated hair has a uniform, livelycurliness and offers and excellently formed, stable permanent wave.

Example 9 Permanent Waving Composition for Normal Hair

7.7 g N-Propyl-2-mercaptoacetamide 8.7 gN-(3′-Hydroxypropyl)-2-mercaptoacetamide 5.0 g Isopropyl alcohol 1.0 g1,2-Propanediol 0.5 g Coconut oil alcohol, ethoxylated with 10 Molethylene oxide 0.5 g Perfume oil 0.1 g Vinylpyrrolidone/styrene mixedpolymer (Antara^(R) 430, GAF Corp., New York) 76.5 g Water 100.0 g ThepH of this composition is 4.5.

Normal hair, not previously damaged, is washed, dried with a hand towel,and wound onto curlers with a diameter of 6 millimeters. After that thehair is moistened thoroughly and evenly with the above-described hairwaving composition. After an action time of 15 to 25 minutes, the hairis rinsed thoroughly with water and then oxidatively post-treated with80 grams of a 3% aqueous hydrogen peroxide solution. After the curlersare taken out, the hair is rinsed again with water, set for a waterwave, and then dried. The thus-treated hair is uniformly curly over theentire length of the hair, which is comparable to the curliness attainedby treatment with mildly alkaline permanent waving compositions.

Example 10 Permanent Waving Composition for Dyed Hair

13.7 g N-(3′-Hydroxypropyl)-2-mercaptoacetamide, 90% strength 4.4 gAmmonia (25% aqueous solution) for pH adjustment 2.0 g Ammonium hydrogencarbonate 2.0 g Dipropyleneglycol monoethyl ester 2.5 g 1,2-Propyleneglycol 1.0 g Poly(dimethyldiallyammonium chloride) 0.3 g Perfume oil 2.5g Phosphoric acid ester of the decyl alcohol ethoxylated with 4 Molethylene oxide (CTFA: DECETH-4 PHOSPHATE) 71.6 g Water 100.0 g The pH ofthis composition is 7.3.

Hair previously damaged by coloring treatments is washed with a shampoo,towel-dried, and set on curlers with a diameter of 8 millimeters. Next,the hair waving composition described above is applied evenly to thehair wound on the curlers. The hair is then covered with a plastic hoodand heated for 10 minutes under a dryer hood at a temperature of 45° C.The covering is then removed; the hair is rinsed with water andoxidatively post-treated with 100 grams of a 3% aqueous hydrogenperoxide solution. After the curlers are taken out, the hair is rinsedagain with water, set for a water wave, and then dried.

The result of this treatment is a uniform, elastic and durable waving ofthe hair.

What is claimed is:
 1. A process for making an N-alkylmercaptoacetamideof formula I:

wherein R represents a straight-chain alkyl group having from 3 to 6carbon atoms or a straight-chain hydroxyalkyl group having from 3 to 6carbon atoms; said process comprising reacting an amine corresponding tosaid N-alkylmercaptoacetamide of the formula (I) withmethylthioglycolate in a reaction mixture under a protective gasatmosphere at a temperature not over 30° C., extracting the reactionmixture with a solvent to form a solvent phase after the reacting andsubsequently removing the solvent from the solvent phase by flashdistillation to obtain said N-alkylmercaptoacetamide.
 2. A compositionfor permanent hair waving, said composition having a pH of 4 to 8.5 andcomprising water, from 3 to 28% by weight of at least oneN-alkylmercaptoacetamide of formula (I) or a salt thereof, as solekeratin-reducing ingredient:

wherein R represents a straight-chain alkyl group having from 3 to 6carbon atoms or a straight-chain hydroxyalkyl group having from 3 to 6carbon atoms; and at least one cosmetic additive ingredient selectedfrom the group consisting of thickeners, solubilizers, anionicsurfactants, cationic surfactants, amphoteric surfactants, nonionicsurfactants, alcohols, opacifiers, perfume oils, dyes, pH adjustingagents, buffer substances, sugars, stabilizers, hair-conditioningingredients and hair-care ingredients; wherein said surfactants, whenpresent, are contained in a total amount of from 0.2 to 30% by weight;said alcohols, when present, are contained in a total amount of from 0.1to 20% by weight; said opacifiers, perfume oils and said dyes, whenpresent, are contained in respective amounts of from 0.01 to 1% byweight; said buffer substances, when present, are contained in a totalamount of from 0.1 to 10% by weight; said sugars, said solubilizers,said stabilizers, said hair conditioning and said hair-care ingredients,when present, are contained in respective amounts of from 0.1 to 5% byweight and said thickeners, when present, are contained in an amount offrom 0.5 to 20% by weight.
 3. The composition as defined in claim 2,wherein said at least one N-alkylmercaptoacetamide isN-propyl-2-mercaptoacetamide, N-(2′-hydroxy -2-mercaptoacetamide orN-(3′-hydroxypropyl)-2-mercaptoacetamide.
 4. A method for permanentwaving of hair, said method comprising the steps of: a) applying acomposition for permanent waving of hair to the hair in an amounteffective for the permanent waving of the hair, said composition forpermanent waving having a pH of 4 to 8.5 and comprising water, from 3 to28% by weight of at least one N-alkylmercaptoacetamide of formula (I) ora salt thereof, as sole keratin-reducing ingredient:

wherein R represents a straight-chain alkyl group having from 3 to 6carbon atoms or a straight-chain hydroxyalkyl group having from 3 to 6carbon atoms; and at least one cosmetic additive ingredient selectedfrom the group consisting of thickeners, solubilizers, anionicsurfactants, cationic surfactants, amphoteric surfactants, nonionicsurfactants, alcohols, opacifiers, perfume oils, dyes, pH adjustingagents, buffer substances, sugars, stabilizers, hair-conditioningingredients and hair-care ingredients; wherein said surfactants, whenpresent, are contained in a total amount of from 0.2 to 30% by weight;said alcohols, when present, are contained in a total amount of from 0.1to 20% by weight; said opacifiers, perfume oils and said dyes, whenpresent, are contained in respective amounts of from 0.01 to 1% byweight; said buffer substances, when present, are contained in a totalamount of from 0.1 to 10% by weight; said sugars, said solubilizers,said stabilizers, said hair conditioning and said hair-care ingredients,when present, are contained in respective amounts of from 0.1 to 5% byweight and said thickeners, when present, are contained in an amount offrom 0.5 to 20% by weight; b) before or after the applying of step a),setting the hair in a desired manner; c) after the applying and thesetting of steps a) and b), rinsing the hair with water; d) after theapplying and the setting of steps a) and b), oxidatively post- treatingthe hair; e) after post-treating the hair oxidatively, rinsing the hairagain with water and drying the hair.
 5. The method as defined in claim4, further comprising allowing said composition for permanent waving toact on the hair for from 5 to 30 minutes prior to said rinsing of thehair with water.
 6. The method as defined in claim 4, further comprisingallowing said composition for permanent waving to act on the hair forfrom 5 to 20 minutes while applying heat to the hair prior to saidrinsing of the hair with water.
 7. The method as defined in claim 4,wherein said amount of said at least one N-alkylmercaptoacetamide offormula (I) is from 60 to 120 grams.
 8. The method as defined in claim4, further comprising putting the hair in a wave after oxidativelypost-treating the hair.